Eliminating turbulence in wall-bounded flows by distorting the flow velocity distribution in a direction perpendicular to the wall

Abstract

For eliminating turbulence in a wall-bounded turbulent flow comprising a flow velocity distribution in a direction perpendicular to the wall, the flow velocity distribution in the direction perpendicular to the wall is distorted. This may be done by locally generating additional vortices in the turbulent flow close to the flow-bounding wall, which are distributed over a section of the flow-bounding wall extending in a main flow direction of the turbulent flow, and whose axes predominantly extend parallel to the flow-bounding wall. Distorting the flow velocity distribution in the direction perpendicular to the wall may also be achieved by increasing the flow velocity close to the flow-bounding wall by locally immersing a flow deviating structure in the turbulent flow, or by equalizing the flow velocity distribution in the direction perpendicular to the wall by locally immersing a flow dividing structure in the turbulent flow.

We claim: 
     
         1 . A method of eliminating turbulence in a wall-bounded turbulent flow comprising a flow velocity distribution in a direction perpendicular to the wall, the method comprising the step of:
 distorting the flow velocity distribution in the direction perpendicular to the wall by locally generating additional vortices in the turbulent flow close to the flow-bounding wall,   wherein the additional vortices are distributed over a section of the flow-bounding wall extending in a main flow direction of the turbulent flow, and   wherein axes of the additional vortices predominantly extend parallel to the flow-bounding wall.   
     
     
         2 . The method of  claim 1 , wherein the additional vortices are generated by injecting fluid into the turbulent flow through the flow-bounding wall, and wherein the fluid is taken from the flow. 
     
     
         3 . The method of  claim 2 , wherein the fluid is injected at a velocity of at least about 25% of an average velocity of the turbulent flow in the main flow direction of the turbulent flow, and wherein the fluid is injected into the flow perpendicularly to the flow-bounding wall. 
     
     
         4 . The method of  claim 1 , wherein the additional vortices are generated with rotationally driven vortex generators immersed in the turbulent flow and distributed over the section of the flow-bounding wall. 
     
     
         5 . The method of  claim 1 , wherein the section of the flow-bounding wall extends
 over a length of the flow which is at least about 15 times a thickness of a boundary layer of the turbulent flow at the flow-bounding wall, or,   with the flow-bounding wall enclosing a lumen through which the turbulent flow flows, over a length of the flow which is at least about 15 times a diameter of the lumen.   
     
     
         6 . An apparatus for eliminating turbulence in a wall-bounded turbulent flow by distorting a flow velocity distribution in a direction perpendicular to the wall, the apparatus comprising:
 a plurality of vortex generators which are
 arranged close to the flow-bounding wall, 
 distributed over a section of the flow-bounding wall extending in a main flow direction of the turbulent flow and 
 configured to generate additional vortices in the turbulent flow whose axes predominantly extend parallel to the flow-bounding wall. 
   
     
     
         7 . The apparatus of  claim 6 , wherein the plurality of vortex generators include at least one of
 nozzles evenly distributed over the section of the flow-bounding wall and configured to inject fluid into the turbulent flow through the flow-bounding wall, and   rotationally driven vortex generators immersed in the turbulent flow.   
     
     
         8 . The apparatus of  claim 6 , wherein the flow-bounding wall, in the section of the flow-bounding wall, downstream of the section of the flow-bounding wall, or both in the and downstream of the section of the flow-bounding wall, is locally covered with a slip material allowing for a velocity of the flow at the boundary to the wall of at least about 40% of an average velocity of the turbulent flow in the main direction of the turbulent flow. 
     
     
         9 . A method of eliminating turbulence in a wall-bounded turbulent flow comprising a flow velocity distribution in a direction perpendicular to the wall, the method comprising the step of:
 distorting the flow velocity distribution in the direction perpendicular to the wall by increasing the flow velocity close to the flow-bounding wall by locally immersing a flow deviating structure in the turbulent flow.   
     
     
         10 . An apparatus for eliminating turbulence in a wall-bounded turbulent flow by distorting a flow velocity distribution in a direction perpendicular to the wall, the apparatus comprising:
 a flow deviating structure immersed in the turbulent flow, the flow deviating being configured to increase the flow velocity close to the flow-bounding wall.   
     
     
         11 . The apparatus of  claim 10 , wherein the flow deviating structure is coaxially arranged in a pipe of circular cross-section, and wherein the flow deviating structure includes at least one of coaxial rings whose radial distances increase towards the flow-bounding wall and a centrally closed flow deviating body formed as a solid of revolution. 
     
     
         12 . A method of eliminating turbulence in a wall-bounded turbulent flow comprising a flow velocity distribution in a direction perpendicular to the wall, the method comprising the step of:
 distorting the flow velocity distribution in the direction perpendicular to the wall by equalizing the flow velocity distribution in the direction perpendicular to the wall by locally immersing a flow dividing structure in the turbulent flow,   the flow dividing structure at least extending over a cross sectional area of the turbulent flow in which flow velocities in the turbulent flow are above an average velocity of the turbulent flow in the main flow direction of the turbulent flow,   the flow dividing structure comprising a plurality of densely packed through holes of constant cross-section,   the through holes extending in the main flow direction of the turbulent flow, and   a length of at least most of the through holes being at least three times its diameter.   
     
     
         13 . The method of  claim 12 , wherein the flow dividing structure extents over the entire turbulent flow, and wherein diameters of all through holes are equal. 
     
     
         14 . The method of  claim 13 , wherein the length of at least some of the through holes is at least five times its diameter. 
     
     
         15 . The method of  claim 13 , wherein the length of each through hole is not more than twenty times its diameter. 
     
     
         16 . The method of  claim 13 , wherein the lengths of the through holes decreases by at least 50% from a center of the turbulent flow towards the wall bounding the flow. 
     
     
         17 . The method of  claim 13 , wherein the diameter of each through hole is at maximum 5% of an average diameter of the turbulent flow. 
     
     
         18 . The method of  claim 13 , wherein the through holes have a circular or hexagonal diameter. 
     
     
         19 . The method of  claim 13 , wherein a porosity of the flow dividing structure is at least 50%. 
     
     
         20 . An apparatus for eliminating turbulence in a wall-bounded turbulent flow by distorting a flow velocity distribution in a direction perpendicular to the wall, the apparatus comprising:
 a flow dividing structure immersed in the flow,   the flow dividing structure being configured to equalize the flow velocity distribution in the direction perpendicular to the wall,   the flow dividing structure at least extending over a cross sectional area of the turbulent flow in which flow velocities in the turbulent flow are above an average velocity of the turbulent flow in the main flow direction of the turbulent flow,   the flow dividing structure comprising a plurality of densely packed through holes of constant cross-section,   the through holes extending in the main flow direction of the turbulent flow, and   the length of at least most of the through holes being at least three times its diameter.   
     
     
         21 . The apparatus of  claim 20 , wherein the flow dividing structure extents over the entire turbulent flow, wherein all the through holes have equal circular or hexagonal diameters, and wherein a porosity of the flow dividing structure is at least 50%. 
     
     
         22 . The apparatus of  claim 20 , wherein the lengths of the through holes decreases by at least 50% from a center of the turbulent flow towards the wall bounding the flow. 
     
     
         23 . The apparatus of  claim 20 , wherein the flow dividing structure comprises one of a bundle of thin-walled tubes, each tube enclosing one of the through holes, and a one-part shaped body enclosing the through holes.